1. Technical Field
The present invention relates to food products. More particularly, the present invention relates to a controlled atmosphere package for produce. In its method aspect, the present invention resides in methods for reducing respiration rates in a controlled manner of produce and for the refrigerated packaging and storage for extended periods.
2. The Prior Art
Present consumer food trends strongly favor increased consumption of fresh food, especially fruits and vegetables. Consumers are preparing increasing amounts of garden salads and fruit salads at home. Restaurants and food service providers are also increasing their offering of vegetable and/or fruit based salads in response to consumer desires.
While consumers find at-home salad consumption is desirable from the standpoint of nutrition, taste, etc., at-home salad preparation is time consuming especially for the small portions of salads typically consumed on a daily basis. For added convenience, cut produce blends suitable for quick salad preparation are available from many grocery stores. However, whether prepared at home or purchased from grocery stores, cut produce whether of one type or blends thereof typically have shelf-lives of only one to a few days. Deterioration of the cut produce is familiar to everyone and is characterized by browning of vegetables proximate their cut portions, wilting, color and flavor loss, loss of crisp texture, mold or rot, and the like.
Maintaining the flavor, texture and eating qualities of produce, from time of harvest through the time of purchase and actual consumption has been a problem of long-standing duration. The most common technique for preventing produce from reaching an over-ripe or deteriorated state has been to pick the produce in a relatively unripe state and to retard the ripening process by the use of refrigeration. Refrigeration is not without problems. For example, tropical and sub-tropical fruits, e.g., bananas are damaged quickly at refrigerated temperatures. Beans, cucumbers and tomatoes can discolor or ripen unevenly below 45.degree. F. Some fruits become more susceptible to microbial attack.
It would be desirable, of course, to be able to extend the storage life of fresh, ripe produce such that the produce could be immediately consumed as well as stored in a ripe state for later consumption. The prior art also includes various packaging and handling techniques for the lengthened storage of whole vegetables and fruits. However, typically whole fruit or vegetable storage shelf life is much greater than cut produce shelf life due to the protective presence of a whole skin or other membranes. The principal mechanisms of decay are mold or fungal attack against the protective skin or cover and enzymatic degradation. Also, cutting produce greatly increases its respiration rate. Accordingly, the teachings with respect to lengthening the storage shelf life of whole fruits and vegetables provides very little practical or valuable guidance for providing packaging for cut produce to extend refrigerated shelf life. Due to the limited shelf life of present cut produce, preparation and sales by grocers of cut produce is primarily locally based. Extended shelf life of at least three weeks would be needed for production and sale on a regional or national scale which could take advantage of economies of scale in produce source procurement, processing, packaging and the like.
Cut produce stored at room temperature deteriorates very rapidly and is unacceptable after only one or two days. Refrigeration can extend shelf life up to about 7 days by reducing respiration rates. Prior efforts both in the U.S. and elsewhere for providing packaged cut produce with extended shelf life, i.e., more than 7 days when stored at refrigerated temperature, have relied upon manipulation of cellular respiration rates and use of chemical preservatives because unlike meat or fish, cut produce is still vital. Once cut off from the supply of nutrients, the cells of the produce contain a limited amount of stored energy. Generally, since cell respiration is also strongly influenced by the immediate atmosphere, one or more of three approaches have been taken to manipulate cellular respiration rates through atmosphere control. One approach is to manipulate and control the initial atmosphere sealed into the package. A second approach is to modify the internal package atmosphere by inclusion of either one or more gas absorbents or scavengers or gas releasants. Finally, the third approach is to control the gas permeability of the packaging material so as to control to ingress or egress of biologically significant gases.
U.S. Pat. No. to R. E. Woodruff 4,411,921 (issued Oct. 25, 1983) is exemplary of the first approach of providing initial atmosphere and discloses incorporation of elevated levels of CO and/or CO.sub.2 with normal or reduced O.sub.2 levels. In U.S. Pat. No. to Cimino 4,411,918, (issued Oct. 25, 1983) et al.) discloses apparatus for preserving food by generating preservative gas. U.S. Pat. No. to Bedrosian et al. 4,423,080 (issued Dec. 27, 1983 ) is exemplary of the second approach using gas absorbents and discloses using packets of chemical agents capable of absorbing moisture and carbon dioxide. Also representative of the absorption approach is U.S. Pat. No. to Nakamura et al. 4,337,276 (issued June 29, 1982 ) which discloses inclusion of zeolite, bentonite and activated carbon for absorption of released ethylene gas.
Representative of using more than one approach, namely controlling both the package gas permeability and providing a controlled initial atmosphere is U.S. Pat. No. to R. E. Woodruff 4,224,347 (issued Sep. 23, 1980 ) which discloses high CO.sub.2 and CO initial levels and packaging material of specified gas permeability.
Notwithstanding the long-standing, widespread and intensive efforts of the prior art, the shelf life of refrigerated packaged cut produce blends to date is limited to at best 7 to 10 days. Modest improvements have been made with regard to longer storage of individual types of cut product. However, extension of shelf life of blends of cut produce with widely varying respiration rates and modes of shelf life failure, e.g., carrots and broccoli, remains in the art a difficult and unresolved problem. Accordingly, there is a continuing need for improved packaged cut produce blend products of extended refrigerated shelf life and method of produce storage and packaging.